1. Field of the Invention
The invention relates generally to the global positioning system (GPS) and more particularly to a GPS information service system for providing GPS location correction and signal acquisition information based upon subscriptions.
2. Description of the Prior Art
The global positioning system (GPS) is used as the basis for many navigation, tracking, survey, geographical information system (GIS), and personal location applications. However, it is not unusual for specialized GPS aiding information to be desired or even required to supplement the GPS system for a particular application. For example, survey and GIS systems require carrier phase or pseudorange correction information to achieve a higher level of precision than can be directly obtained from the GPS system. Personal location systems may require assistance in order to achieve the signal sensitivity that is needed for signal acquisition in indoor locations.
Most applications of GPS can benefit from GPS acquisition information for faster signal acquisition. Unfortunately, the services for providing GPS aiding information are limited to specific types of information for specific types of GPS receivers. There is no existing method or apparatus for providing the broad range of supplemental GPS aiding information that is desired or needed by the various types of GPS receivers for the various applications.